Conventionally, several methods have been known for producing a benzochalcogenophene derivative.
For example, NON-PATENT DOCUMENTS 1 and 2 disclose a method for synthesizing a benzochalcogenophene derivative by reacting sodium sulfide with a 2-halogeno-1-acetylene derivative in ethanol.
NON-PATENT DOCUMENT 3 discloses a method for synthesizing [1]benzochalcogeno[3,2-b][1]benzochalcogenophene by reacting tert-butyllithium with bis(2-bromophenyl)acetylene at low temperature in THF (tetrahydrofuran) solvent, followed by addition of sulfur, selenium, or tellurium. However, problems of operational safety and extreme difficulty in industrial application exist because tert-butyllithium ignites when reacted with water in the air.
NON-PATENT DOCUMENT 4 discloses a method for synthesizing a benzothiophene derivative characterized by reacting butyllithium with a 2-bromo-acetylene derivative. However, questions of operational safety and industrial application are similarly raised because alkyllithium is used in this method. Accordingly, establishment of a safer and industrially applicable method for producing the compound has been demanded.
NON-PATENT DOCUMENT 5 discloses a method for producing a trithienobenzene derivative from dibromothiophene through three steps. However, the current reality is that the above method is far from a safe industrial production method because raw materials are expensive, and further, butyllithium is used in two steps and reacted at ultra-low temperature.    NON-PATENT DOCUMENT 1: Synthesis, (13), 2131-2134 (2004)    NON-PATENT DOCUMENT 2: ARKIVOC (Gainesville, Fla., United States), (13), 87-100 (2003)    NON-PATENT DOCUMENT 3: Journal of Organic Chemistry 70(25), 10569-10571 (2005)    NON-PATENT DOCUMENT 4: Organic Letters, 3(5), 651-654 (2001)    NON-PATENT DOCUMENT 5: Organic Letters, 6(2), 273-276 (2004)